Process for inhibiting corrosion of metals



new

United States Patent PROCESS FOR INHIBITING CORROSION 0F METALS Donald L. Andersen, Minneapolis, Minn., assign'or to General Mills, Inc., a corporation of Delaware No Drawing. Application August 30, 1957 Serial No. 681,183

2 Claims. (Cl. 117127) This invention relates to a new process for corrosion inhibition of metallic substances. This process may be employed in aqueous-oil systems, in finished petroleum products, in protective coating, and in industrial water systems.

Corrosion of metallic substances represents a major industrial problem. Every year the loss to industry through corrosion amounts to millions of dollars. In general, this corrosion takes place when the metallic substances, especially ferrous-containing metals, come in contact with a watery media, i.e., water, aqueous solutions, water vapor, and the like. Various methods are presently known and utilized for preventing or inhibiting the corrosive activity of the various aqueous media. The most frequently employed method for inhibiting and preventing corrosion is to cover the surface of the metallic substance with a protective coating.

It has now been discovered that a tenacious protective film of essentially mono-molecular dimensions having corro'sion inhibition properties is formed when one of the compounds of the general structural formula where R is hydrogen or a lower alkyl group containing less than four carbon atoms, R is a high molecular weight, straight or branched chained, hydrocarbon radical containing 8 to 22 carbon atoms, X is hydrogen or an alkali metal, and Y is an alkaline earth metal, comes in contact with the metallic surface to be protected. These compounds are readily available commercial compounds. All may be classified as substituted products of beta-amino propionate where the hydrocarbon radical, R'-, is derived from various high molecular weight acids and contains the same number of carbon atoms as the original acid. Common sources of these acids are rosin acids and the fatty acids such as those obtained from tall oil, soybean oil, coconut oil, cottonseed oil, linseed oil, soap stock, safflower oil, castor oil, tallow, lard, and other fats and oils. It will be appreciated that the acids contained from each source are generally a complex mixture, which are, for all intents and purposes, relatively uniform in composition. Thus, R'is defined in many of the folice lowing compounds according to the source of the original acids, i.e., coco-coco'nut oil, ta1low-tallow, rosinrosin acids, and so forth.

A unique application of this discovery is the use of .these compounds in wire drawing as a combination lubricant and corrosion inhibitor. Fatty acids are extensively utilized as lubricants in this process and may be used in combination with the corrosion inhibitors of this invention. I Another advantage to the use of these compounds as corrosion inhibitors "lies in the fact that they are known surfactants. For instance, they are especially useful surface active agents for incorporation in shampoo formulations and when employed in aerosols contained. in metal cans, they serve the dual purpose of surfactant in the shampoo and protect the metal aerosol can from corrosion during storage.

These anti-corrosive characteristics make them useful additives in all detergent compositions packaged in metallic containers.

This invention may be-illustrated further by reference to the following examples in which all parts are expressed as parts by weight and all percentages are expressed as percent by weight, unless specified otherwise.

EXAMPLE I In the Navy static water drop testno rust resulted when sodium N-coco-beta-aminopropionate was employed at a concentration of 0.1%. 7

- Similar resultswere obtained using 0.1% of disodium N-tallow beta-iminodipropiohate EXAMPLE III The following results were obtained using the ASTM D-665 turbine oil rusting test:

Concen- Inhibitor tration, Results percent (1) sodium N-coeo-beta aminopropionate.. 0.1 very light rust. (2) disodium N-tallow-beta lminopropb 0. 1 Do.

onate.

O. 1 no rust. 0.0067 Do. (3) Sodium N-tallow-alpha-methyl-beta- 0.005 D0.

aminoproplonate. 0. 0033 very light rust.

0. 0017' light rust.

3 EXAMPLE IV The following results were obtained using the NACE screening test:

Concentration (Parts Percent Inhibitor per million Inhibiin water) tion 25 07 (1) sodium N-coco-beta aminopropionate 1g (2) sodium N-tallow-beta aminopropionate is (3) sodium N-hydrogenatedtallow-beta-amino- 25 95 pruninn ate 10 82 25 94 (4) sodium N-rosin-bets-aminopropionate 1(5) 3% 25 95 (5) sodium N-tallow oil-beta aminopropionate 1(5) l (6) disodium N-dodeeyl-beta-iminopropionate. 25 86 (7) disodium N tallow-betaiminopropionate- (8) disodium N-soy-betaimlnopropionate 10 77 (9) sodium N -coco-beta-methyl-beta-amino- 100 95 propionate. (1o disodium N-tallow-beta-methyl-betaaminopropionate 5 70 (11) sodium N -coco-alpha-methyl-betaaaminog 3% propionate 2 74 (12) sodium N-coco-beta-methyl-beta-amino- 3g propionate 2 64 (13) sodium N-tallow-alpha-methyl-beta-aminopropionate 10 89 (14) disodium N -tallow-beta iminodibutyrate--- 10 89 (Parts per million in oil) (15) caleium-di-N-tallow-beta-aminopropionate-.. 75 91 (16) sodium N-tallow-beta-methyl-beta-amino- 28 propionate 40 62 EXAMPLE V Table I shows the efiectiveness of various compounds as corrosion inhibitors as measured qualitatively at 75 parts per million in a sealed static water test. The testing procedure was conducted as follows:

Step A: 1"X 1"X A6" S.A.E. 1020 mild steel coupons having a diameter hole were pickled as follows (1) Soak coupons in reagent grade acetone and dry in 3.11. (2) Pickle 10.0 min. in concentrated HCl at room temperature with agitation. (3) Rinse in distilled water, acetone dip, and dry at reduced pressure in a desiccator.

Step B: Suspend each coupon from a Pyrex hook in 150 mliml. of test solution (prepared from distilled water to 75 p.p.m. inhibitoril p.p.m. based on 100% active material) so as to be fully immersed with the coupons top edge A" to below test solution surface using 250 ml. Pyrex Erlenmeyer flasks as the test container.

Step C: Leave the coupon suspended for three daysitwo hours at room temperature.

Step D: Remove coupons from test flasks and visually observe the condition of the coupon.

Many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

Now, therefore, I claim:

1. A process for corrosion inhibition of metallic substances which comprises covering said metallic substance with a mono-molecular film of a compound selected from the group consists of Where R is selected from the group consisting of hydrogen and lower alkyl radicals containing less than four carbon atoms, R is a hydrocarbon radical containing 8 to 22 carbon atoms, X is selected from the group consisting of hydrogen and an alkali metal, and Y is an alkaline earth metal.

2. A process for corrosion inhibition of metallic substances which comprises covering said metallic substances with a mono-molecular film of a compound having the general formula, R'NHCR CR COOX where R is a straight chain hydrocarbon radical containing 8 to 22 carbon atoms, R is hydrogen or a lower alkyl radical containing less than five carbon atoms, and X is an alkali metal.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,012 Isbell Apr. 19, 1949 2,736,658 Pfohl et al. Feb. 28, 1956 2,840,890 Emm July 1, 1958 2,842,837 Huet et al. July 15, 1958 

1. A PROCESS FOR CORROSION INHIBITION OF METALLIC SUBSTANCES WHICH COMPRISES COVERING SAID METTALIC SUBSTANCE WITH A MONO-MOLECULAR FILM OF A COMPOUND SELECTED FROM THE GROUP CONSISTS OF 